Octane

So I have a code 42 for the idle switch on my 1995 JDM WRX motor in my wagon which I'm struggling to clear.

The manual states: 

42 Idle switch -  Abnormal voltage input entered from idle switch  - "Judges OFF operation"

My understanding is that the idle switch is part of the throttle position sensor, and when the throttle position sensor shows a certain position (voltage), it will trigger the idle switch in the ECU.

I have changed out the TPS with a brand new OEM one and set the TPS correctly at 0.7v at closed and 4.5v at fully open (could be the other way around, i cant remember) and this cured my original TPS fault, but not the Idle Switch fault.

The issue I'm having is that when I set the idle switch correctly as per this: 

it sets the voltages incorrectly for the TPS and it'll throw both the TPS and an O2 sensor fault.

I've tried multiple ECU resets, and I've also cleaned the IACV and TPS with contact cleaner along with the appropriate connections and plugs. I've also tested continuity for the TPS wiring back to the ECU and found no issues there.

None of the stopper screws have been touched on the throttle manifold, and the throttle cable isn't over-tensioned or anything.

Its possible I have a slight leak in the intake which I will fix tomorrow, but otherwise I'm out of ideas.

Can anyone shed some light on things?